Chapter 8

Meninges, ventricular system and blood supply

MENINGES

Basic anatomy

Dura mater

Arachnoid mater

Pia mater

Function of the meninges

THE VENTRICULAR SYSTEM

Basic anatomy

Ventricles

Cerebrospinal fluid

Function of the ventricular system

CIRCULATORY SYSTEMS OF THE BRAIN

Arterial supply

Basic anatomy

Function of the arterial supply

The blood–brain barrier

Venous drainage

Basic anatomy

Function of venous drainage

Meninges

Basic anatomy

The brain and spinal cord are surrounded by three membranes termed ‘meninges’, which primarily protect and cushion the brain, brain stem and spinal cord.

Dura mater

This outer layer is conventionally described as two layers, however they are closely united except along certain lines where they part to surround and support large venous channels termed ‘the dural venous sinuses’ (Fig. 8.1). The two layers comprise:

Figure 8.1 The ventricular system showing a dural venous sinus.

The endosteal layer, which represents the periosteum covering the inner surface of the skull bones.

The meningeal layer, which is the dura mater proper. This is a thick, dense, strong fibrous sheet covering the brain and it is continuous with the dura mater of the brain stem and spinal cord.

Arachnoid mater

This middle layer is a delicate web-like structure lying between the dura mater and pia mater. The space between the dura mater externally and the arachnoid mater is called the ‘subdural space’. The space between the pia mater internally and the arachnoid mater is the ‘subarachnoid space’. The major arteries to the brain pass through the subarachnoid space and it is also filled with cerebrospinal fluid. This space extends down the spinal cord to the level of the second sacral vertebra.

In certain areas, the arachnoid mater projects into the dural venous sinuses to form arachnoid villi or granulations (Fig. 8.1) via which cerebrospinal fluid is recycled into the venous blood system.

Pia mater

This inner layer is a very delicate impermeable vascular membrane closely covering the brain surface (Fig. 8.1).

Function of the meninges

The outermost covering, the dura mater, serves to protect the underlying nervous tissue of the central nervous system and also has a role in restricting the displacement of the brain during head movement.

The primary function of the arachnoid mater and the space enclosing the cerebrospinal fluid is to further cushion the central nervous system. The pia mater supports capillaries that enter the tissue of the cerebral hemispheres.

The ventricular system

Basic anatomy

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